Lemon

Uses

Pharmacologically, lemon is primarily important for its vitamin C nutritional value and for its potassium content. Epidemiological studies associate the intake of citrus fruit with a reduction in the risk of various diseases. Antioxidant and anticancer actions are being investigated, and a role in hypocitraturic calcium nephrolithiasis has been suggested. Lemon also shows some antimicrobial activity.

Contraindications

Pregnancy/Lactation

Generally recognized as safe when used as food. Avoid dosages above those found in food because safety and efficacy are unproven.

Interactions

Chloroquine plasma concentrations may be reduced; iron absorption may be increased.

Adverse Reactions

Erosive effects on tooth enamel and anaphylactic allergy to lemon soap have been reported. Citrus juice is often implicated in the worsening of gastroesophageal reflux disease symptoms.

Toxicology

Research reveals little or no information regarding toxicology.

Botany

The lemon tree is an evergreen, growing to over 6 m in height. Its toothed leaves are light green and the citrus fruit (lemon) is oval, small, and green to yellow. Unlike other citrus varieties, the lemon tree bears fruit continuously. The plant is cultivated in Mediterranean and subtropical climates worldwide. 1 , 2 , 3

History

The lemon originated in Southeast Asia, probably in India or southern China. Its history is sometimes unclear because of the confusion with the similarly appearing citron, a closely related species. The lemon may have been depicted in Roman artwork as early as the first century AD. 3

In the 1600s, physicians became aware that daily intake of lemon juice would prevent outbreaks of scurvy among sailors on long sea voyages. English ships were required by law to carry enough lemon or lime juice for each sailor to get 1 ounce daily, earning them the nickname “limeys.” 4

The California lemon industry became established after the gold rush of 1849. From 1940 to 1965, production increased and the United States became a major provider of lemons. More than 50% of the US lemon crop is processed into juice and other drink products. The peel, pulp, and seeds are used to make oils, pectin, or other products. 3

Lemon juice has long been used as an astringent, diaphoretic, diuretic, gargle, lotion, and tonic. 3 Application of lemon juice in conjunction with exposure to sunlight was once thought to fade tattoos, but this theory was disproven. 5 Lemon has also been used externally for acne, fungus (ringworm and athlete's foot), sunburn, and warts. 2

Uses and Pharmacology

Pharmacologically, the lemon is primarily important for its vitamin C and potassium content. Epidemiological studies associate the intake of citrus fruit with a reduction in the risk of various diseases. 13 , 16 , 17

Antioxidant effects

German studies in the late 1980s related this effect to the peel. 4 The pectin fiber and lemon oil also possess antioxidant properties. 18

One group of researchers, having identified eriocitrin, hesperidin, and coumarins as antioxidants, pursued experiments in diabetic rats, 14 and venous endothelial cells, 10 as well as in activated Epstein-Barr virus models. 11 Antioxidant mechanisms include the inhibition of radical formation and radical scavenging. 10 , 11 , 13 Clinical trials are lacking.

Cancer

In an experiment with the flavonoid eriocitrin and its metabolites 19 and with coumarins extracted from lemon fruit, 11 apoptosis has been demonstrated in acute myelomonocytic leukemia cells.

A meta-analysis of epidemiological studies associates the consumption of citrus fruit with a larger protective effect against oral cancer (odds ratio [per doc] 0.38; 95% confidence interval 0.26 to 0.56) than with overall fruit consumption. 17 The structure of various chemical constituents of lemon and their relationship to cancer prevention has been investigated. 13 , 20

Lemon juice and lemon oil have been evaluated for antimicrobial action. The oil shows some bacteriostatic and antiviral action thought to be due to citral and linalool content. 12 , 13 Lemon has been shown to inhibit the growth of Aspergillus mold, 23 and has been used to disinfect drinking water 24 and to inactivate rabies virus. 25

The sperm-immobilizing properties of lemon juice have been investigated as a potential topical vaginal contraceptive. 26 Lemon juice accelerated the transit of tetrofosmin through the liver parenchyma and improved myocardial imaging in a small study. 27

Adverse Reactions

Anaphylactic allergy to lemon soap has been reported resulting from a possible cross sensitivity of citrus seed to peanut allergen. 33

Citrus juice is often implicated in the worsening of gastroesophageal reflux disease symptoms. However, no effect on lower esophageal sphincter pressure was demonstrated in a small study, and the effects are not considered to be related to fruit juice acidity. 34

Toxicology

Research reveals little or no information regarding toxicology with the use of lemon.